Protein requirements of juvenile freshwater crayfish Cherax quadricarinatus, with initial mean weight of 1.08 ± 0.34 g, were studied. Juveniles were fed experimental diets containing seven levels of crude protein (CP) (20, 25, 31, 37, 43, 49, and 55%) and 18.73–21.45 kJ  g−1 of gross energy. The highest mean weight and specific growth rate (SGR) (P < 0.05), with values of 9.6 g, and 3.64% day−1, respectively, were achieved by feeding a diet of 31% CP. This diet resulted in a survival rate of 80% over 60 days of culture at 27 °C. The higher protein level tested (55% CP), yielded a significantly (P < 0.05) lower mean weight of 6.4 g. However, there were no significant differences in SGR among the 20, 25, and 49% CP diets. Feed Conversion Ratio (FCR) was close to 1 for all treatments except the lowest (20%) and highest (55%) CP. Optimum protein requirements were estimated by fitting mean weight gain data to a quadratic model (y = 1.142+0.484 − 0.0071x2, r2 = 0.952, P < 0.05). Optimal growth occurred with 34.2% CP, but the results suggest that optimum protein level for 1‐g juvenile C. quadricarinatus is 31% in least‐cost diets. The information obtained will contribute to the formulation of diets that will enhance production of C. quadricarinatus.

This study determined the effect of different dietary protein and lipid levels on growth and survival of juvenile redclaw Cherax quadricarinatus. Nine practical test diets were formulated to contain three crude protein (CP) levels [260, 310 and 360 g kg−1, equivalent to 225, 260 and 296 g kg−1 digestible protein (DP) respectively] at three crude lipid (CL) levels (40, 80 and 120 g kg−1, equivalent to 38, 67 and 103 digestible lipids respectively), with digestible protein : digestible energy (DP : DE) ranging from 14.6 to 22.6 mg protein kJ g−1. Three replicate groups of 15 crayfish (initial weight mean ± SD, 0.71 ± 0.13 g) per diet treatment were stocked in 40 L tanks, at 28 °C for 60 days. The highest mean weight, specific growth rate and biomass, with values of 7.0 g, 3.67% day−1, and 370.2 g m−2, respectively, were achieved by feeding a diet with P : L = 310 : 80 (P < 0.05). The treatments resulted in a survival rate of 80–91%, feed conversion ratio of 1.08–1.61 and protein efficiency ratio of 2.24–3.08. Results indicated that a diet containing 270 g kg−1 DP (equivalent to 320 g kg−1 CP), 75 g kg−1 digestible lipid (DL) with a DP/DE of 18.4 mg protein kJ−1, and 0.031 g protein per animal per day was optimum for juvenile C. quadricarinatus under the tested experimental conditions.

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Feeding trials with five levels of crude protein (CP) (22%, 27%, 33%, 39%, and 45%) and digestible energy ranging from 14.32 to 15.21 kJ g−1 were carried out to determine optimum dietary protein for the growth and production of pre‐adult freshwater crayfish Cherax quadricarinatus. Triplicate groups of males (ω=23.1±0.58 g) and females (ω=21.8±0.33 g) were fed diets for 70 days in monosex culture. Optimal digestible protein (DP) was estimated for males by fitting mean weight gain to a quadratic model (y=27.86+0.839x–0.0216x2, r2=0.945), and a linear model for females (y=32.84–0.0745x, r2=0.959). Optimal male growth occurred with 25.6% CP, equivalent to 19.4% DP. Male crayfish attained significantly higher final weights and absolute growth rate than females fed the 22%, 27%, and 33% CP diets. The results indicated that a 19.4% DP diet, with a P/E ratio of 11.4 mg kJ−1, produces an optimum growth response for pre‐adult C. quadricarinatus under experimental conditions.

We determined the effect of four concentrations of dietary crude protein, 30.7, 37.2, 41.8 and 46.8% on growth rate, survival and body composition of the juvenile cauque river prawn (Macrobrachium americanum). The prawns were hatched in the laboratory from the spawn of one wild ovigerous female. Prawns consuming 37.2% crude protein reached a final weight of 0.58 g (feed conversion ratio of 2.15), which was significantly better than the other treatments. Survival was 100% in all treatments. Protein content in the diets had no significant effect on whole body proximate composition and amino acid profile. Juveniles consuming the 37.2% crude protein diet grew faster than those fed the other diets. Specific growth rate was adjusted to the two-slope broken-line regression analysis model to estimate the optimal protein requirement. In conclusion, these results demonstrated that the 37.2% protein level diet is optimal for juvenile cauque river prawn M. americanum in the experimental conditions of this study.